Fix Image.create_from_data use_mipmaps doc

The Image.create_from_data doc describes the "use_mipmaps" argument as a
way to generate mipmaps, but this method only allocates and loads data.
This can cause confusion, where this function reads more or less data
than expected. Update the doc to be more specific that create_from_data
is loading the mipmaps from the raw data.

(cherry picked from commit 09b324b5b6b956efb2b4a60bd73916bbaf6ff10f)

doc/classes/Image.xml

@@ -142,7 +142,7 @@
 			<argument index="4" name="data" type="PoolByteArray">
 			</argument>
 			<description>
-				Creates a new image of given size and format. See [enum Format] constants. Fills the image with the given raw data. If [code]use_mipmaps[/code] is [code]true[/code] then generate mipmaps for this image. See the [method generate_mipmaps].
+				Creates a new image of given size and format. See [enum Format] constants. Fills the image with the given raw data. If [code]use_mipmaps[/code] is [code]true[/code] then loads mipmaps for this image from [code]data[/code]. See [method generate_mipmaps].
 			</description>
 		</method>
 		<method name="crop">